spellmaster decryptor

spellmaster.py

"""
PT/CT pairs

Key       expanded    Plaintext                      Ciphertext
AAAAAAAA  AAAAAAAA    AAAAAAAAAA                     VTPL?DL?HV
AAAAAAAA  AAAAAAAA    ABCDEFGHIJKLMNOPQRSTUVWXY      VMHTL?QFPCBKSZCJGRZM-EEEZ
AAAA      AAAAAAAA    BBBB                           OTBZ
AAAAAAAA  AAAAAAAA    BBBBBBBBBB                     OTBZNRZNVA
AAAAAAAA  AAAAAAAA    BBBBBBBBBBBBBBBB               OTBZNRZNVAJRJFVR
AAA       AAAAAAAA    BBBBBBBBBBBBBBBBBBBBBBBBB      OTBZNRZNVAJRJFVRVVOTVBBJB
AAAAAAAA  AAAAAAAA    BCDEFGHIJKLMNOPQRSTUVWXYZ      OLXXXIRHMTOWV-JWBPCGQEIFY
AAAAAAAA  AAAAAAAA    CDEFGHIJKLMNOPQRSTUVWXYZA      GN?HEJTIUVSJOV-ZLVFSUYZEH
AAAAAAAA  AAAAAAAA    DEFGHIJKLMNOPQRSTUVWXYZAB      ABHIRHMYSZVONCRTFEJSUZAHA
AAAAAAAA  AAAAAAAA    IS-SPELLMASTER-ALIVE?          PRQGBETNKDV?EHYE-RELK
BBBBBBBB  BBBBBBBB    IS-SPELLMASTER-ALIVE?          XERHCFUOLZWAFIZF?SM-L 
CAT       CATCATCA    DOGSDOGSDOGSDOGS               QLGAGVHPOCWEXCID
CATS      CATSCATS    DOGSDOGSDOGSDOGS               WXCQ-DSUCEKQD-WU
SECRECY   SECRECYS    CRYPTOMUSEUM-FOREVER           LRCHZHE-GQBBSJROQ--R
SECRECY   SECRECYS    LONG-LIVE-CRYPTOMUSEUM         ?HIJVVI-XLXOKRKI?SKIQX

see  https://www.reddit.com/r/codes/comments/wa8g4i/cryptomuseum_is_looking_for_help_in_figuring_out/

Code by [email protected].

https://github.com/nlitsme

"""
def umod28(c):
    c %= 28
    if c<0: c += 28
    return c

def umod26(c):
    c %= 26
    if c<0: c += 26
    return c

def to28(x):
    return x.replace('-', '[').replace('?', '\\')
def from28(x):
    return x.replace('[', '-').replace('\\', '?')

def smod256(c):
    c %= 256
    if c<-128: c += 256
    if c>127: c -= 256
    return c



class SpellMasterCipher:
    def __init__(self, key = None):
        if key is None:
            key = "FRANKLIN"
        while len(key) < 8:
            key = key + key
        self.key = key[:8]

        self.DecodeXlate = [ 3, 12, 16, 10, 9, 22, 11, 0, 20, 6, 14, 24, 5, 8, 1, 18, 17, 7, 4, 15, 19, 25, 2, 13, 21, 23, 26, 27 ]
        self.EncodeXlate = [ 7, 14, 22, 0, 18, 12, 9, 17, 13, 4, 3, 6, 1, 23, 10, 19, 2, 16, 15, 20, 8, 24, 5, 25, 11, 21, 26, 27 ]

    def encode(self, text):
        # Convert input text to 0-27 range
        word_buf = [ self.EncodeXlate[ord(c)-ord('A')] for c in text ]
  
        # Take copy of the key
        tempcode = [ ord(c) for c in self.key ]
  
        # Encrypt the text
        result = []
        for c in word_buf:
  
            # Calculate key
            key = umod26(smod256((sum(tempcode) - 8 * ord('A'))))
           
            # Apply key
            result.append( umod26(key - c) )
           
            # Modify key
            key = umod26(key + c)
           
            tempcode = tempcode[1:] + [ key ]
  
        return "".join(chr(c+ord('A')) for c in result)

    def decode(self, text):
        # Convert input text to 0-27 range
        word_buf = [ ord(c)-ord('A') for c in text ]
     
        # Take copy of the key
        tempcode = [ ord(c) for c in self.key ]
     
        # decrypt the text
        result = []
        for c in word_buf:
     
            # Calculate key
            key = umod26(smod256((sum(tempcode) - 8 * ord('A'))))
     
            # Apply key
            result.append( umod26(key - c) )
     
            # Modify key
            key = umod26(key + result[-1])
           
            tempcode = tempcode[1:] + [ key ]
         
        # Convert result back to ASCII range
        return "".join(chr(self.DecodeXlate[c]+ord('A')) for c in result)


def main():
    import argparse
    parser = argparse.ArgumentParser(description='spellmaster decrypt')
    parser.add_argument('--key', '-k', type=str)
    parser.add_argument('--decrypt', '-d', action='store_true')
    parser.add_argument('--encrypt', '-e', action='store_true')
    parser.add_argument('--sm26', action='store_true', help='code from the patent')
    parser.add_argument('textdata', nargs='*', type=str)

    args = parser.parse_args()

    if not args.sm26:
        global umod26
        umod26 = umod28   # ... not the prettiest solution here....

    sm = SpellMasterCipher(args.key)
    for txt in args.textdata:
        if not args.sm26:
            txt = to28(txt)
        if args.decrypt:
            res = sm.decode(txt)
        else:
            res = sm.encode(txt)
        if not args.sm26:
            res = from28(res)
        print(res)


if __name__ == '__main__':
    main()

testvectors.sh

python3 spellmaster.py -e -k    AAAAAAAA      AAAAAAAAAA
python3 spellmaster.py -e -k    AAAAAAAA      ABCDEFGHIJKLMNOPQRSTUVWXY
python3 spellmaster.py -e -k    AAAA          BBBB
python3 spellmaster.py -e -k    AAAAAAAA      BBBBBBBBBB
python3 spellmaster.py -e -k    AAAAAAAA      BBBBBBBBBBBBBBBB
python3 spellmaster.py -e -k    AAA           BBBBBBBBBBBBBBBBBBBBBBBBB
python3 spellmaster.py -e -k    AAAAAAAA      BCDEFGHIJKLMNOPQRSTUVWXYZ
python3 spellmaster.py -e -k    AAAAAAAA      CDEFGHIJKLMNOPQRSTUVWXYZA
python3 spellmaster.py -e -k    AAAAAAAA      DEFGHIJKLMNOPQRSTUVWXYZAB
python3 spellmaster.py -e -k    AAAAAAAA      IS-SPELLMASTER-ALIVE?
python3 spellmaster.py -e -k    BBBBBBBB      IS-SPELLMASTER-ALIVE?
python3 spellmaster.py -e -k    CAT           DOGSDOGSDOGSDOGS
python3 spellmaster.py -e -k    CATS          DOGSDOGSDOGSDOGS
python3 spellmaster.py -e -k    SECRECY       CRYPTOMUSEUM-FOREVER
python3 spellmaster.py -e -k    SECRECY       LONG-LIVE-CRYPTOMUSEUM


python3 spellmaster.py -d -k    AAAAAAAA      VTPL?DL?HV
python3 spellmaster.py -d -k    AAAAAAAA      VMHTL?QFPCBKSZCJGRZM-EEEZ
python3 spellmaster.py -d -k    AAAA          OTBZ
python3 spellmaster.py -d -k    AAAAAAAA      OTBZNRZNVA
python3 spellmaster.py -d -k    AAAAAAAA      OTBZNRZNVAJRJFVR
python3 spellmaster.py -d -k    AAA           OTBZNRZNVAJRJFVRVVOTVBBJB
python3 spellmaster.py -d -k    AAAAAAAA      OLXXXIRHMTOWV-JWBPCGQEIFY
python3 spellmaster.py -d -k    AAAAAAAA      GN?HEJTIUVSJOV-ZLVFSUYZEH
python3 spellmaster.py -d -k    AAAAAAAA      ABHIRHMYSZVONCRTFEJSUZAHA
python3 spellmaster.py -d -k    AAAAAAAA      PRQGBETNKDV?EHYE-RELK
python3 spellmaster.py -d -k    BBBBBBBB      XERHCFUOLZWAFIZF?SM-L
python3 spellmaster.py -d -k    CAT           QLGAGVHPOCWEXCID
python3 spellmaster.py -d -k    CATS          WXCQ-DSUCEKQD-WU
python3 spellmaster.py -d -k    SECRECY       LRCHZHE-GQBBSJROQ--R
python3 spellmaster.py -d -k    SECRECY       ?HIJVVI-XLXOKRKI?SKIQX